This invention relates to a thin film formation technique and equipment that can control the flux and speed of a molecular beam.
In accordance with a conventional thin film formation technique, a desired material is placed in a boat-like container and is then heated so that the material atoms are evaporated and stuck on a substrate prepared in advance, and thickness control of the thin film is made using a quartz oscillator or the like disposed close to the substrate. Where control of film thickness with a high level of resolution is necessary such as in a molecular beam epitaxy equipment, a Knudsen cell has been often used as a molecular beam source (evaporation source) of the element. In the Knudsen cell, the total molecular beam flux is determined if the temperature of the molecular source is set, and since the spatial distribution of effusion follows a Cosine Law, the molecular beam flux reaching the substrate is determined if the geometrical structure is determined. In this case, a quartz oscillator is conjointly used for monitor. (See, for example, S. Yamamoto et al., J. Appl. Phys. 46 (1975) 406).
However, the thin film formation technique described above does not directly measure the molecular beam reaching the substrate, so that the technique can not control the energy or speed of the molecular beam. Furthermore, since the mutual relation between the quantity of the molecular beam reaching the substrate and the quantity of the molecular beam participating in the film formation, that is, sticking probability, is not clear, control of film thickness can not be made completely.